This invention relates to laser devices, and more particularly to a device for preventing the destruction of the reflecting surface of a resonator mirror in a laser due to electrical discharges from one of the discharge electrodes.
Gas lasers such as the powerful CO.sub.2 laser have an anode and a cathode with an electrical discharge between them for activating the laser medium. Aligned with the electrical discharge is a pair of optical resonator mirrors between which light oscillations occur. Precision mirrors used as resonator mirrors include a thin coat, typically of an electrically nonconducting material.
A problem which now exists with lasers like this is that in addition to the discharge between the anode and the cathode, discharges between the cathode and the coated mirror surface also occur if the relative potentials between these components are varied, as for example during initiation or termination of the discharge. This problem is especially serious when the discharge is pulse modulated. This occurs as a result of electrical charge transfer between the mirrored surface and the cathode. These electrical discharges are very serious since they cause a deterioration of optical property of the mirror.